Pure Appl. Chem., 71, 1593-1607 (1999) (errata) (The values are unchanged from the 1995 table [Pure Appl. Chem., 68, 2339-2359 (1996)], but incorporates the approved names for elements 101-109 [Pure Appl. Chem., 69, 2471-2473 (1997)], recognises element 112 and adjusts the range of atomic weight for lithium.). See also the 2001 table for more recent values.
https://iupac.qmul.ac.uk/AtWt/
World Wide Web version of atomic weight data prepared by G. P. Moss, originally from a file provided by D. R. Lide.
The 1995 table resulted in changes in the standard values and/or error for B, C, F, Na, Al, P, Sc, Mn, Co, As, Rh, Cs, Ce, Pr, Eu, Tb, Ho, Tm, Pt, Au and Bi. See also the 1993 table
The original paper should be consulted for details of the half life of the radioisotopes quoted below. In addition there are recommendations on the scales for quoting relative isotope-ratio data for stable hydrogen, lithium, carbon, oxygen and sulfur. Also there is a report on the different isotopic compositions of some non-terrestrial materials.
A number in parentheses indicates the uncertainty in the last digit of the atomic weight.
See also a copy of the periodic table with atomic weights to five significant figures.
See also below the list in Name order.
At No | Symbol | Name | Atomic Wt | Notes |
1 | H | Hydrogen | 1.00794(7) | 1, 2, 3 |
2 | He | Helium | 4.002602(2) | 1, 2 |
3 | Li | Lithium | 6.941(2) | 1, 2, 3, 4 |
4 | Be | Beryllium | 9.012182(3) | |
5 | B | Boron | 10.811(7) | 1, 2, 3 |
6 | C | Carbon | 12.0107(8) | 1, 2 |
7 | N | Nitrogen | 14.00674(7) | 1, 2 |
8 | O | Oxygen | 15.9994(3) | 1, 2 |
9 | F | Fluorine | 18.9984032(5) | |
10 | Ne | Neon | 20.1797(6) | 1, 3 |
11 | Na | Sodium | 22.989770(2) | |
12 | Mg | Magnesium | 24.3050(6) | |
13 | Al | Aluminium | 26.981538(2) | |
14 | Si | Silicon | 28.0855(3) | 2 |
15 | P | Phosphorus | 30.973761(2) | |
16 | S | Sulfur | 32.066(6) | 1, 2 |
17 | Cl | Chlorine | 35.4527(9) | 3 |
18 | Ar | Argon | 39.948(1) | 1, 2 |
19 | K | Potassium | 39.0983(1) | 1 |
20 | Ca | Calcium | 40.078(4) | 1 |
21 | Sc | Scandium | 44.955910(8) | |
22 | Ti | Titanium | 47.867(1) | |
23 | V | Vanadium | 50.9415(1) | |
24 | Cr | Chromium | 51.9961(6) | |
25 | Mn | Manganese | 54.938049(9) | |
26 | Fe | Iron | 55.845(2) | |
27 | Co | Cobalt | 58.933200(9) | |
28 | Ni | Nickel | 58.6934(2) | |
29 | Cu | Copper | 63.546(3) | 2 |
30 | Zn | Zinc | 65.39(2) | |
31 | Ga | Gallium | 69.723(1) | |
32 | Ge | Germanium | 72.61(2) | |
33 | As | Arsenic | 74.92160(2) | |
34 | Se | Selenium | 78.96(3) | |
35 | Br | Bromine | 79.904(1) | |
36 | Kr | Krypton | 83.80(1) | 1, 3 |
37 | Rb | Rubidium | 85.4678(3) | 1 |
38 | Sr | Strontium | 87.62(1) | 1, 2 |
39 | Y | Yttrium | 88.90585(2) | |
40 | Zr | Zirconium | 91.224(2) | 1 |
41 | Nb | Niobium | 92.90638(2) | |
42 | Mo | Molybdenum | 95.94(1) | 1 |
43 | Tc | Technetium | [98] | 5 |
44 | Ru | Ruthenium | 101.07(2) | 1 |
45 | Rh | Rhodium | 102.90550(2) | |
46 | Pd | Palladium | 106.42(1) | 1 |
47 | Ag | Silver | 107.8682(2) | 1 |
48 | Cd | Cadmium | 112.411(8) | 1 |
49 | In | Indium | 114.818(3) | |
50 | Sn | Tin | 118.710(7) | 1 |
51 | Sb | Antimony | 121.760(1) | 1 |
52 | Te | Tellurium | 127.60(3) | 1 |
53 | I | Iodine | 126.90447(3) | |
54 | Xe | Xenon | 131.29(2) | 1, 3 |
55 | Cs | Caesium | 132.90545(2) | |
56 | Ba | Barium | 137.327(7) | |
57 | La | Lanthanum | 138.9055(2) | 1 |
58 | Ce | Cerium | 140.116(1) | 1 |
59 | Pr | Praseodymium | 140.90765(2) | |
60 | Nd | Neodymium | 144.24(3) | 1 |
61 | Pm | Promethium | [145] | 5 |
62 | Sm | Samarium | 150.36(3) | 1 |
63 | Eu | Europium | 151.964(1) | 1 |
64 | Gd | Gadolinium | 157.25(3) | 1 |
65 | Tb | Terbium | 158.92534(2) | |
66 | Dy | Dysprosium | 162.50(3) | 1 |
67 | Ho | Holmium | 164.93032(2) | |
68 | Er | Erbium | 167.26(3) | 1 |
69 | Tm | Thulium | 168.93421(2) | |
70 | Yb | Ytterbium | 173.04(3) | 1 |
71 | Lu | Lutetium | 174.967(1) | 1 |
72 | Hf | Hafnium | 178.49(2) | |
73 | Ta | Tantalum | 180.9479(1) | |
74 | W | Tungsten | 183.84(1) | |
75 | Re | Rhenium | 186.207(1) | |
76 | Os | Osmium | 190.23(3) | 1 |
77 | Ir | Iridium | 192.217(3) | |
78 | Pt | Platinum | 195.078(2) | |
79 | Au | Gold | 196.96655(2) | |
80 | Hg | Mercury | 200.59(2) | |
81 | Tl | Thallium | 204.3833(2) | |
82 | Pb | Lead | 207.2(1) | 1, 2 |
83 | Bi | Bismuth | 208.98038(2) | |
84 | Po | Polonium | [209] | 5 |
85 | At | Astatine | [210] | 5 |
86 | Rn | Radon | [222] | 5 |
87 | Fr | Francium | [223] | 5 |
88 | Ra | Radium | [226] | 5 |
89 | Ac | Actinium | [227] | 5 |
90 | Th | Thorium | 232.0381(1) | 1, 5 |
91 | Pa | Protactinium | 231.03588(2) | 5 |
92 | U | Uranium | 238.0289(1) | 1, 3, 5 |
93 | Np | Neptunium | [237] | 5 |
94 | Pu | Plutonium | [244] | 5 |
95 | Am | Americium | [243] | 5 |
96 | Cm | Curium | [247] | 5 |
97 | Bk | Berkelium | [247] | 5 |
98 | Cf | Californium | [251] | 5 |
99 | Es | Einsteinium | [252] | 5 |
100 | Fm | Fermium | [257] | 5 |
101 | Md | Mendelevium | [258] | 5 |
102 | No | Nobelium | [259] | 5 |
103 | Lr | Lawrencium | [262] | 5 |
104 | Rf | Rutherfordium | [261] | 5, 6 |
105 | Db | Dubnium | [262] | 5, 6 |
106 | Sg | Seaborgium | [263] | 5, 6 |
107 | Bh | Bohrium | [264] | 5, 6 |
108 | Hs | Hassium | [265] | 5, 6 |
109 | Mt | Meitnerium | [268] | 5, 6 |
110 | Uun | Ununnilium | [269] | 5, 6 |
111 | Uuu | Unununium | [272] | 5, 6 |
112 | Uub | Ununbium | [277] | 5, 6 |
At No | Symbol | Name | Atomic Wt | Notes |
89 | Ac | Actinium | [227] | 5 |
13 | Al | Aluminium | 26.981538(2) | |
95 | Am | Americium | [243] | 5 |
51 | Sb | Antimony | 121.760(1) | 1 |
18 | Ar | Argon | 39.948(1) | 1, 2 |
33 | As | Arsenic | 74.92160(2) | |
85 | At | Astatine | [210] | 5 |
56 | Ba | Barium | 137.327(7) | |
97 | Bk | Berkelium | [247] | 5 |
4 | Be | Beryllium | 9.012182(3) | |
83 | Bi | Bismuth | 208.98038(2) | |
107 | Bh | Bohrium | [264] | 5, 6 |
5 | B | Boron | 10.811(7) | 1, 2, 3 |
35 | Br | Bromine | 79.904(1) | |
48 | Cd | Cadmium | 112.411(8) | 1 |
55 | Cs | Caesium | 132.90545(2) | |
20 | Ca | Calcium | 40.078(4) | 1 |
98 | Cf | Californium | [251] | 5 |
6 | C | Carbon | 12.0107(8) | 1, 2 |
58 | Ce | Cerium | 140.116(1) | 1 |
17 | Cl | Chlorine | 35.4527(9) | 3 |
24 | Cr | Chromium | 51.9961(6) | |
27 | Co | Cobalt | 58.933200(9) | |
29 | Cu | Copper | 63.546(3) | 2 |
96 | Cm | Curium | [247] | 5 |
105 | Db | Dubnium | [262] | 5, 6 |
66 | Dy | Dysprosium | 162.50(3) | 1 |
99 | Es | Einsteinium | [252] | 5 |
68 | Er | Erbium | 167.26(3) | 1 |
63 | Eu | Europium | 151.964(1) | 1 |
100 | Fm | Fermium | [257] | 5 |
9 | F | Fluorine | 18.9984032(5) | |
87 | Fr | Francium | [223] | 5 |
64 | Gd | Gadolinium | 157.25(3) | 1 |
31 | Ga | Gallium | 69.723(1) | |
32 | Ge | Germanium | 72.61(2) | |
79 | Au | Gold | 196.96655(2) | |
72 | Hf | Hafnium | 178.49(2) | |
108 | Hs | Hassium | [265] | 5, 6 |
2 | He | Helium | 4.002602(2) | 1, 2 |
67 | Ho | Holmium | 164.93032(2) | |
1 | H | Hydrogen | 1.00794(7) | 1, 2, 3 |
49 | In | Indium | 114.818(3) | |
53 | I | Iodine | 126.90447(3) | |
77 | Ir | Iridium | 192.217(3) | |
26 | Fe | Iron | 55.845(2) | |
36 | Kr | Krypton | 83.80(1) | 1, 3 |
57 | La | Lanthanum | 138.9055(2) | 1 |
103 | Lr | Lawrencium | [262] | 5 |
82 | Pb | Lead | 207.2(1) | 1, 2 |
3 | Li | Lithium | 6.941(2) | 1, 2, 3, 4 |
71 | Lu | Lutetium | 174.967(1) | 1 |
12 | Mg | Magnesium | 24.3050(6) | |
25 | Mn | Manganese | 54.938049(9) | |
109 | Mt | Meitnerium | [268] | 5, 6 |
101 | Md | Mendelevium | [258] | 5 |
80 | Hg | Mercury | 200.59(2) | |
42 | Mo | Molybdenum | 95.94(1) | 1 |
60 | Nd | Neodymium | 144.24(3) | 1 |
10 | Ne | Neon | 20.1797(6) | 1, 3 |
93 | Np | Neptunium | [237] | 5 |
28 | Ni | Nickel | 58.6934(2) | |
41 | Nb | Niobium | 92.90638(2) | |
7 | N | Nitrogen | 14.00674(7) | 1, 2 |
102 | No | Nobelium | [259] | 5 |
76 | Os | Osmium | 190.23(3) | 1 |
8 | O | Oxygen | 15.9994(3) | 1, 2 |
46 | Pd | Palladium | 106.42(1) | 1 |
15 | P | Phosphorus | 30.973761(2) | |
78 | Pt | Platinum | 195.078(2) | |
94 | Pu | Plutonium | [244] | 5 |
84 | Po | Polonium | [209] | 5 |
19 | K | Potassium | 39.0983(1) | 1 |
59 | Pr | Praseodymium | 140.90765(2) | |
61 | Pm | Promethium | [145] | 5 |
91 | Pa | Protactinium | 231.03588(2) | 5 |
88 | Ra | Radium | [226] | 5 |
86 | Rn | Radon | [222] | 5 |
75 | Re | Rhenium | 186.207(1) | |
45 | Rh | Rhodium | 102.90550(2) | |
37 | Rb | Rubidium | 85.4678(3) | 1 |
44 | Ru | Ruthenium | 101.07(2) | 1 |
104 | Rf | Rutherfordium | [261] | 5, 6 |
62 | Sm | Samarium | 150.36(3) | 1 |
21 | Sc | Scandium | 44.955910(8) | |
106 | Sg | Seaborgium | [263] | 5, 6 |
34 | Se | Selenium | 78.96(3) | |
14 | Si | Silicon | 28.0855(3) | 2 |
47 | Ag | Silver | 107.8682(2) | 1 |
11 | Na | Sodium | 22.989770(2) | |
38 | Sr | Strontium | 87.62(1) | 1, 2 |
16 | S | Sulfur | 32.066(6) | 1, 2 |
73 | Ta | Tantalum | 180.9479(1) | |
43 | Tc | Technetium | [98] | 5 |
52 | Te | Tellurium | 127.60(3) | 1 |
65 | Tb | Terbium | 158.92534(2) | |
81 | Tl | Thallium | 204.3833(2) | |
90 | Th | Thorium | 232.0381(1) | 1, 5 |
69 | Tm | Thulium | 168.93421(2) | |
50 | Sn | Tin | 118.710(7) | 1 |
22 | Ti | Titanium | 47.867(1) | |
74 | W | Tungsten | 183.84(1) | |
112 | Uub | Ununbium | [277] | 5, 6 |
110 | Uun | Ununnilium | [269] | 5, 6 |
111 | Uuu | Unununium | [272] | 5, 6 |
92 | U | Uranium | 238.0289(1) | 1, 3, 5 |
23 | V | Vanadium | 50.9415(1) | |
54 | Xe | Xenon | 131.29(2) | 1, 3 |
70 | Yb | Ytterbium | 173.04(3) | 1 |
39 | Y | Yttrium | 88.90585(2) | |
30 | Zn | Zinc | 65.39(2) | |
40 | Zr | Zirconium | 91.224(2) | 1 |